/*
Copyright 2011 Google Inc. All Rights Reserved.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/

package com.google.rsm.core;

/**
 * An implementation of {@code Event} that implements {@link
 * Event#getType} with instance equality semantics, guaranteeing that
 * all instances of this class will have different types in the state
 * machine.
 *
 * <p>It achieves this by returning itself as its own {@code
 * EventType}.  Derived classes must take care to implement {@code
 * hashCode} and {@code equals} with instance equality semantics,
 * meaning no two instances will compare equally, and most will have
 * different hash codes. The default implementations provided by
 * {@code Object} is usually enough.
 *
 * <p>A convenient side effect of this implementation is that instances
 * implement the {@link EventType} interface and can be passed to
 * methods in the state machine framework that expect one.
 *
 * @author arunabhaghosh@google.com (Arunabha Ghosh)
 */
public class InstanceEvent implements Event, EventType {
  /**
   * {@inheritDoc}
   *
   * Returns {@code this}.
   */
  @Override
  public EventType getType() {
    return this;
  }
}
